linux-kernel - Re: [PATCH] EDAC, mc: Fix edac_mc_find() in case no device is found

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Message-ID: <20190514094317.GB31140@zn.tnic>
Date:   Tue, 14 May 2019 11:43:17 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Robert Richter <rrichter@...vell.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        James Morse <james.morse@....com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] EDAC, mc: Fix edac_mc_find() in case no device is found

On Tue, May 14, 2019 at 07:25:58AM +0000, Robert Richter wrote:
> The function should return NULL in case no device is found, but it
> always returns the last checked mc device from the list even if the
> index did not match. This patch fixes this.
> 
> I did some analysis why this did not raise any issues for about 3
> years and the reason is that edac_mc_find() is mostly used to search
> for existing devices. Thus, the bug is not triggered.
> 
> Fixes: c73e8833bec5 ("EDAC, mc: Fix locking around mc_devices list")
> Signed-off-by: Robert Richter <rrichter@...vell.com>
> ---
>  drivers/edac/edac_mc.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/edac/edac_mc.c b/drivers/edac/edac_mc.c
> index 13594ffadcb3..aeeaaf30b38a 100644
> --- a/drivers/edac/edac_mc.c
> +++ b/drivers/edac/edac_mc.c
> @@ -688,10 +688,9 @@ struct mem_ctl_info *edac_mc_find(int idx)
>  		mci = list_entry(item, struct mem_ctl_info, link);
>  
>  		if (mci->mc_idx >= idx) {
> -			if (mci->mc_idx == idx) {
> -				goto unlock;
> -			}
> -			break;
> +			if (mci->mc_idx != idx)
> +				mci = NULL;
> +			goto unlock;
>  		}
>  	}

Can we simplify this silly code even more pls? I'm pasting the whole
function instead of a diff for clarity:

---
struct mem_ctl_info *edac_mc_find(int idx)
{
        struct mem_ctl_info *mci = NULL;
        struct list_head *item;

        mutex_lock(&mem_ctls_mutex);

        list_for_each(item, &mc_devices) {
                mci = list_entry(item, struct mem_ctl_info, link);
                if (mci->mc_idx == idx)
                        goto unlock;
        }

        mci = NULL;

unlock:
        mutex_unlock(&mem_ctls_mutex);
        return mci;
---

Thx.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.